A conventional present day axial flow gas turbine engine normally comprises, in axial flow sequence, a compressor section, a combustor (which may be radially disposed), in which compressed air from the high pressure compressor is mixed with fuel and burnt, and a turbine section driven by the products of combustion. In the case of an aeroengine (excluding turboshaft aeroengines), all the power developed by the turbine section is used to drive the compressor section, which can include a fan propulsor. In the case of a turboshaft engine, or an engine adapted for electrical power generation or marine propulsion, the turbine section has an upstream part which is used to drive the compressor section, and a downstream part comprising a power turbine on a power offtake shaft which rotates independently of the rest of the turbine section.
Note that in the present specification, the terms "upstream" and "downstream" refer to the direction of compressed air and combustion gas flows through the axial flow compressors and turbines of axial flow gas turbine engines. Hence, for a component associated with a main gas passage of such a turbine or compressor, the upstream direction is towards the front of the engine and the downstream direction is towards its rear.
The products of combustion pass from the combustor through discharge nozzles to the first stage of the turbine through an array of nozzle guide vanes. These nozzle guide vanes must be supported and located both axially and radially to cope with the dynamic and thermal loads occurring during engine operation.
The downstream end of the combustor must also be located and supported in such a way that it can cope with the dynamic and thermal loads which occur during engine operation. Furthermore, the support and location of the nozzle guide vanes and the downstream portion of the combustor should be such that loads applied to nozzle guide vanes do not impose loads upon the downstream portion of the combustor and vice versa.